I own the 3 CD sets published by Edsel records that only countains the mono version of some of the score for the cult British Series. I aquired a couple years ago the French 45rpm of The New Avengers opening theme. It contains a special version of the theme, with a super funky electric guitare on top of it (the best version if you ask me).
On Face B, in the track called "A flavour of the New Avengers" We get a compilation of samples from the score along with Sir Patrick Macnee's voice over. https://www.youtube.com/watch?v=_UsYhzbegSM&t=1s
These samples are in stereo. Which makes me beleive there are stereo master tapes somewhere, waiting to be remastered and released to the fans.
(It's less likely the older seasons have stereo recordings).
The New Avengers show was the least interesting of all the seasons but had an amazing funky soundtrack. This is one of my holly grails.
There doesn't seem to have been much of the original music located at the time they did those Edsel sets - both the set for The Avengers and the one for The New Avengers were disappointing in terms of content and sound quality (as was the set dedicated for The Professionals, actually...)
It's also never been possible to buy a CD version of the re-recorded gatefold LP that Johnson did for Unicorn-Kanchana called MUSIC FROM THE AVENGERS, THE NEW AVENGERS AND THE PROFESSIONALS. There was a Varese/Starlog version of the Avengers/New Avengers cues, but leaving off The Professionals selections, (which I think only appeared on a bootleg and which were sourced from the LP).
I believe that certainly more Avengers material has surfaced and I hope someone else releases this in the future. I'd also hope (but remain sceptical) that the original New Avengers cues might be found - as you say, funky stuff indeed
On Face B, in the track called "A flavour of the New Avengers" We get a compilation of samples from the score along with Sir Patrick Macnee's voice over. https://www.youtube.com/watch?v=_UsYhzbegSM&t=1s